Two-pipe enhanced-vapor-injection outdoor unit and multi-split system

ABSTRACT

A two-pipe enhanced-vapor-injection outdoor unit and a multi-split system are provided. The two-pipe enhanced-vapor-injection outdoor unit includes: an outdoor heat exchanger; a compressor including a gas discharge port, the gas return port and an injection port; a reversing assembly including a first end connected with the gas discharge port, and a second end connected with the gas return port; a flash evaporator comprising a refrigerant inlet, a gas outlet and a liquid outlet, the gas outlet being connected with the injection port, the liquid outlet being connected with the first port and the inlet of the outdoor heat exchanger, respectively; a throttling assembly including a first end connected with the refrigerant inlet, and a second end connected with the second port; and a first pipe.

The present disclosure is based on and claims priority to Chinese Patent Application No. 201811227632.6, filed on Oct. 22, 2018, the entire content of which is incorporated herein by reference.

FIELD

The present disclosure relates to a technical field of refrigeration, and particularly to a two-pipe enhanced-vapor-injection outdoor unit and a two-pipe enhanced-vapor-injection multi-split system.

BACKGROUND

Currently, the conventional enhanced vapor injection and low-temperature forced heat change technologies are only used in the heat pump and the three-pipe heat recovery system. Since the gas return pipe of the outdoor unit in the two-pipe system just has the low pressure, it is difficult to achieve the enhanced vapor injection at the injection port of the compressor. Thus, the two-pipe multi-split system has the low pressure at the low-pressure side, the low density of the returned gas, and the small refrigerant circulation, and hence has the problem of insufficient heating capacity in the low-temperature environment, due to the low environment temperature. Moreover, the two-pipe system has problems of the high exhaust superheat degree and the insufficient heating capacity in the high-pressure environment.

SUMMARY

The present disclosure intends to at least solve one of the technical problems existing in the related art.

An aspect of the present disclosure provides a two-pipe enhanced-vapor-injection outdoor unit.

Another aspect of the present disclosure provides a two-pipe enhanced-vapor-injection multi-split system.

In view of the above, the present disclosure provides a two-pipe enhanced-vapor-injection outdoor unit. The two-pipe enhanced-vapor-injection outdoor unit includes: an outdoor heat exchanger, a first port and a second port; an enhanced-vapor-injection compressor including a gas discharge port, a gas return port and an injection port; a reversing assembly including a first end connected with the gas discharge port, and a second end connected with the gas return port; a flash evaporator including a refrigerant inlet, a gas outlet and a liquid outlet, the gas outlet being connected with the injection port, the liquid outlet being connected with the first port and an inlet of the outdoor heat exchanger, respectively; a throttling assembly including a first end connected with the refrigerant inlet, and a second end connected with the second port; a first pipe including a first end connected with an outlet of the outdoor heat exchanger, and a second end arranged between the throttling assembly and the second port.

The two-pipe enhanced-vapor-injection outdoor unit provided by the present disclosure includes the outdoor heat exchanger, the first port, the second port, the enhanced-vapor-injection compressor, the reversing assembly, the flash evaporator, the throttling assembly and the first pipe. The first end of the reversing assembly is connected with the gas discharge port, and the second end of the reversing assembly is connected with the gas return port. The gas outlet of the flash evaporator is connected with the injection port, and the liquid outlet of the flash evaporator is connected with the first port and the inlet of the outdoor heat exchanger, respectively. The refrigerant inlet of the flash evaporator is connected with the first end of the throttling assembly, and the second end of the throttling assembly is connected with the second port. The first end of the first pipe is connected with the outlet of the outdoor heat exchanger, and the second end of the first pipe is arranged between the throttling assembly and the second port. In the present disclosure, by using the enhanced-vapor-injection compressor, the gaseous refrigerant flowing out of the enhanced-vapor-injection heat exchanger directly enters the compressor through the middle injection port of the compressor for the enhanced-vapor-injection compression. Moreover, the flash evaporator and the throttling assembly are added to significantly increase a refrigerant circulation in a heating operation at a low temperature, such that a range of the heating operation at the low temperature is expanded in the two-pipe enhanced-vapor-injection outdoor unit, and also the heating capacity is improved significantly, so as to achieve purposes of improving the cooling capacity at a high temperature and reducing an exhaust superheat degree.

In addition, the first pipe is added, such that the effect of enhanced vapor injection can be obtained in four modes, namely, a cooling mode, a heating mode, a main cooling mode and main heating mode.

The flash evaporator is a container that can hold the refrigerant, and usually has three ports, namely the refrigerant inlet for entrance of the refrigerant gas-liquid mixture, the gas outlet for the refrigerant and the liquid outlet for the refrigerant. The flash evaporator has following working principles: the gas-liquid mixture of the refrigerant from the upstream throttling element flows in through the refrigerant inlet of the flash evaporator; due to the sudden expansion of the volume, a large amount of refrigerant flashes out from the liquid refrigerant, becomes the refrigerant gas with a low temperature, and flows out of the gas outlet; and the liquid refrigerant which has not flashed flows out of the flash evaporator from the liquid outlet. Thus, there are not any droplets at the gas outlet of the flash evaporator, and there is not any gas at the liquid outlet.

Since the gas outlet of the flash evaporator is connected to the injection port, it can be ensured that the refrigerant discharged from the gas outlet is a gaseous refrigerant during the enhanced vapor injection, which effectively prevents the problem of liquid impact of the enhanced-vapor-injection compressor, and guarantees the service life of the enhanced-vapor-injection compressor.

The two-pipe enhanced-vapor-injection outdoor unit is a two-pipe structure, and two connection pipes are provided between an indoor unit and the outdoor unit. That is, the first port and the second port are connected with the indoor unit. Compared with the three-pipe multi-split system in the related art, the two-pipe heat-recovery multi-split system provided by the present disclosure has a simple structure, such that the cupper materials are saved, and the mounting cost is reduced.

In addition, the two-pipe enhanced-vapor-injection outdoor unit provided by the present disclosure is used in the two-pipe enhanced-vapor-injection multi-split system, and the multi-split system is a heat-recovery multi-split system. The heat recovery means that the heat discharged from the cooling room is recovered for heating of the heating room. Specifically, the system uses the indoor-unit heat exchanger to absorb heat from the cooling room, then the indoor-unit heat exchanger releases such heat completely or partially to the heating room for heating, and the heat lacked by the system or the remaining heat of the system is obtained from the environment by the outdoor-unit heat exchanger. However, for the ordinary heat-pump multi-split system, the heat required by the heating indoor unit totally comes from the heat absorption and the power consumption of the outdoor-unit heat exchanger. Thus, compared with the ordinary heat pump, the heat-recovery multi-split system has a significant energy-saving effect.

The heat-recovery multi-split system includes four operation modes, namely a cooling mode, a main cooling mode, a main heating mode and a heating mode. When all the operating indoor units are in the cooling mode/the heating mode, the outdoor unit operates in the cooling mode/the heating mode. When a part of the operating indoor units are in the cooling mode, another part of the operating indoor units are in the heating mode, and the cooling load is greater than the heating load, the outdoor unit will operate in the main cooling mode. When a part of the operating indoor units are in the cooling mode, another part of the operating indoor units are in the heating mode, and the cooling load is less than the heating load, the outdoor unit will operate in the main heating mode. If the flow rate required for running the cooling indoor units is exactly equal to the flow rate required for running the heating indoor units, the system operates in a full heat-recovery mode.

In addition, the two-pipe enhanced-vapor-injection outdoor unit according to the above technical solutions of the present disclosure further includes following additional technical features.

In any of the above technical solutions, preferably, the third end of the reversing assembly is switchably connected to the inlet of the outdoor heat exchanger or the outlet of the outdoor heat exchanger, and the fourth end of the reversing assembly is switchably connected to the second port or the first port.

In this technical solution, the third end of the reversing assembly is switchably connected to the inlet of the outdoor heat exchanger or the outlet of the outdoor heat exchanger, and the fourth end of the reversing assembly is switchably connected to the second port or the first port. When the two-pipe enhanced-vapor-injection multi-split system is in the cooling mode and the main cooling mode, the third end of the reversing assembly is connected to the inlet of the outdoor heat exchanger, and the fourth end of the reversing assembly is connected to the second port. When the two-pipe enhanced-vapor-injection multi-split system is in the heating mode and the main heating mode, the third end of the reversing assembly is connected to the outlet of the outdoor heat exchanger, and the fourth end of the reversing assembly is connected to the first port, so as to achieve different flow directions of the refrigerant.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a first solenoid valve arranged the gas outlet and the injection port, and having a conduction direction from the gas outlet to the injection port 166.

In this technical solution, the two-pipe enhanced-vapor-injection outdoor unit includes the first solenoid valve. The first solenoid valve is conducted when powered on, and is closed when powered off. When the first solenoid valve is powered on to be conducted, the conduction direction of the first solenoid valve is from the gas outlet to the injection port, i.e. a conduction direction, in which the refrigerant is only allowed to flow from the gas outlet to the injection port, so as to avoid the refrigerant backflow phenomenon.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes a first check valve disposed in the first pipe, and the first check valve has a conduction direction from the outlet of the outdoor heat exchanger to the throttling assembly.

In this technical solution, by adding the first pipe, the outlet of the outdoor heat exchanger and the throttling assembly are connected. The first check valve is arranged in the first pipe, and is added between the outlet of the outdoor heat exchanger and the throttling assembly, so as to prevent the gas from being exchanged between the outlet of the outdoor heat exchanger and the throttling assembly during heating, such that only in the cooling mode and the main cooling mode, the refrigerant flowing out of the outlet of the outdoor heat exchanger is allowed to flow through the first check valve into the throttling assembly, while in the heating mode and the main heating mode, the first check valve is closed, and thus the refrigerant flowing out of the outlet of the outdoor heat exchanger cannot pass through the first pipe.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a second check valve, the second check valve connecting the first port with the liquid outlet, and having a conduction direction from the liquid outlet to the first port; and a third check valve, the third check valve connecting the second port to the throttling assembly, and having a conduction direction from the second port to the throttling assembly.

In this technical solution, the two-pipe enhanced-vapor-injection outdoor unit includes the second check valve, and the conduction direction of the second check valve is form the liquid outlet to the first port. A first end of the second check valve is arranged between the liquid outlet and the inlet of the outdoor heat exchanger, and a second end of the second check valve is connected with the first port. In the cooling mode and the main cooling mode, the second check valve is turned on, such that the refrigerant flowing out of the liquid outlet of the flash evaporator flows through the second check valve to the first port. In the heating mode and the main heating mode, the second check valve is closed, and the refrigerant flowing out of the liquid outlet of the flash evaporator cannot pass through the second check valve, but can only pass through the inlet of the outdoor heat exchanger.

Further, the two-pipe enhanced-vapor-injection outdoor unit includes the third check valve, and the conduction direction of the third check valve is from the second port to the throttling assembly. In the heating mode and the main heating mode, the third check valve is turned on, and the refrigerant flowing out of the second port passes through the third check valve to the throttling assembly. In the cooling mode and the main cooling mode, the third check valve is closed, and the refrigerant flowing out of the first pipe can only flow to the throttling assembly.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a fourth check valve, the fourth check valve connecting the second port to the fourth end of the reversing assembly, and having a conduction direction from the second port to the fourth end of the reversing assembly; and a fifth check valve, the fifth check valve connecting the first port to the fourth end of the reversing assembly, and having a conduction direction from the fourth end of the reversing assembly to the first port.

In this technical solution, the two-pipe enhanced-vapor-injection outdoor unit includes the fourth check valve and the fifth check valve. The fourth check valve connects the second port to the fourth end of the reversing assembly, and the conduction direction of the fourth check valve is from the second port to the fourth end of the reversing assembly. The fifth check valve connects the first port to the fourth end of the reversing assembly, and the conduction direction of the fifth check valve is from the fourth end of the reversing assembly to the first port. During operations in the cooling mode and the main cooling mode, the fourth check valve is conducted, and the fifth check valve is closed. During operations in the heating mode and the main heating mode, the fifth check valve is conducted, and the fourth check valve is closed.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a sixth check valve, the sixth check valve connecting the third end of the reversing assembly to the inlet of the outdoor heat exchanger, and having a conduction direction from the third end of the reversing assembly to the outdoor heat exchanger; and a seventh check valve, the seventh check valve connecting the third end of the reversing assembly to the outlet of the outdoor heat exchanger, and having a conduction direction from the outlet of the outdoor heat exchanger to the third end of the reversing assembly.

In this technical solution, the two-pipe enhanced-vapor-injection outdoor unit includes the sixth check valve and the seventh check valve. The sixth check valve and the fifth check valve are both connected with the third end of the reversing assembly, and the other ends of the sixth check valve and the seventh check valve are connected with the inlet of the outdoor heat exchanger and the outlet of the outdoor heat exchanger, respectively. During operations in the cooling mode and the main cooling mode, the sixth check valve is conducted, and the seventh check valve is closed. During operations in the heating mode and the main heating mode, the seventh check valve is conducted, and the sixth check valve is closed.

In any of the above technical solutions, preferably, the throttling assembly includes at least one throttling device and at least one eighth check valve connected in series, and the eighth check valve has a conduction direction from the second port to the refrigerant inlet.

In this technical solution, the throttling assembly includes the at least one throttling device and the at least one eighth check valve connected in series. The conduction direction of the eighth check valve is from the supercooler to the inlet of the outdoor heat exchanger. One throttling device may be connected in series with one eighth check valve, or one throttling device may be connected in series with a plurality of eighth check valves, or a plurality of throttling devices may be connected in series with one eighth check valve, so as to ensure the effects of throttling and depressurization, and thus a better depressurization effect can be achieved after multi-stage depressurizations.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a second pipe connecting the gas discharge port to the first port; and a second solenoid valve arranged in the second pipe, and having a conduction direction from the gas discharge port to the first port.

In this technical solution, the two-pipe enhanced-vapor-injection outdoor unit includes the second pipe and the second solenoid valve arranged in the second pipe. During the operation in the cooling mode, the second solenoid valve is closed, and all the refrigerant discharged from the gas discharge port passes through the third end of the reversing assembly into the inlet of the outdoor heat exchanger. During the operation in the main cooling mode, the second solenoid valve is turned on, a part of the refrigerant discharged from the gas discharge port passes through the third end of the reversing assembly into the inlet of the outdoor heat exchanger, and another part of the refrigerant discharged from the gas discharge port passes through the second solenoid valve into the first port, so as to ensure that the two-pipe enhanced-vapor-injection multi-split system can achieve the cooling mode and the main cooling mode.

In any of the above technical solutions, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes a ninth check valve, the ninth check valve connects the inlet of the outdoor heat exchanger to the liquid outlet, and has a conduction direction from the liquid outlet to the inlet of the outdoor heat exchanger.

In this technical solution, the two-pipe enhanced-vapor-injection outdoor unit includes the ninth check valve, and the conduction direction of the ninth check valve is from the liquid outlet to the inlet of the outdoor heat exchanger. In the cooling mode and the main cooling mode, the ninth check valve is closed, and the refrigerant flowing out of the liquid outlet of the flash evaporator cannot pass through the ninth check valve into the inlet of the outdoor heat exchanger, but can only pass through the pipe, where the second check valve is, into the first port. In the heating mode and the main heating mode, the ninth check valve is turned on, and the refrigerant flowing out of the liquid outlet of the flash evaporator passes through the ninth check valve into the inlet of the outdoor heat exchanger.

According to an aspect of the present disclosure, a two-pipe enhanced-vapor-injection multi-split system is provided. The two-pipe enhanced-vapor-injection multi-split system includes the two-pipe enhanced-vapor-injection outdoor unit according to any of the above technical solutions. Therefore, the two-pipe enhanced-vapor-injection multi-split system has all the significant effects of the two-pipe enhanced-vapor-injection outdoor unit according to any of the above technical solutions.

Additional aspects and advantages of embodiments of present disclosure will be given in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following descriptions made with reference to the drawings, in which:

FIG. 1 illustrates a schematic view of a two-pipe enhanced-vapor-injection multi-split system provided by an embodiment of the present disclosure;

FIG. 2 illustrates another schematic view of a two-pipe enhanced-vapor-injection multi-split system provided by an embodiment of the present disclosure;

FIG. 3 illustrates a schematic view of a two-pipe enhanced-vapor-injection multi-split system in a cooling mode provided by an embodiment of the present disclosure;

FIG. 4 illustrates a schematic view of a two-pipe enhanced-vapor-injection multi-split system in a heating mode provided by an embodiment of the present disclosure;

FIG. 5 illustrates a schematic view of a two-pipe enhanced-vapor-injection multi-split system in a main cooling mode provided by an embodiment of the present disclosure;

FIG. 6 illustrates a schematic view of a two-pipe enhanced-vapor-injection multi-split system in a main heating mode provided by an embodiment of the present disclosure;

FIG. 7 illustrates a pressure-enthalpy diagram of a two-pipe enhanced-vapor-injection multi-split system provided by an embodiment of the present disclosure.

REFERENCE NUMERALS

Reference numerals in FIG. 1 to FIG. 6 have following corresponding relationships with names of parts.

10 outdoor heat exchanger, 12 first port, 14 second port, 16 enhanced-vapor-injection compressor, 162 gas discharge port, 164 gas return port, 166 injection port, 18 reversing assembly, 20 flash evaporator, 202 refrigerant inlet, 204 gas outlet, 206 liquid outlet, 22 throttling assembly, 222 throttling device, 224 eighth check valve, 24 first pipe, 26 first solenoid valve, 28 first check valve, 30 second check valve, 32 third check valve, 34 fourth check valve, 36 fifth check valve, 38 sixth check valve, 40 seventh check valve, 42 second solenoid valve, 44 ninth check valve, 46 two-pipe enhanced-vapor-injection indoor unit, 48 refrigerant-flow-direction switching direction, 50 gas-liquid separator, 52 first supercooler, 54 second supercooler.

DETAILED DESCRIPTION

In order to clearly understand the above objectives, features and advantages of the present disclosure, the present disclosure is further described in detail with reference to the accompanying drawings and specific embodiments. It is to be noted that, in the case of no conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other.

In the following descriptions, many specific details are set forth so as to provide a thorough understanding of the present disclosure. However, the present disclosure may be implemented in other manners other than what are described herein. The scope protection of the present disclosure is not limited by the specific embodiments disclosed below.

A two-pipe enhanced-vapor-injection outdoor unit and a two-pipe enhanced-vapor-injection multi-split system according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 7.

As illustrated in FIGS. 1 to 6, the two-pipe enhanced-vapor-injection outdoor unit provided by the present disclosure includes: an outdoor heat exchanger 10, a first port 12 and a second port 14; an enhanced-vapor-injection compressor 16 including a gas discharge port 162, a gas return port 164 and an injection port 166; a reversing assembly 18 including first to fourth ends, the first end of the reversing assembly 18 being connected with the gas discharge port 162, the second end of the reversing assembly 18 being connected with the gas return port 164; a flash evaporator 20 including a refrigerant inlet 202, a gas outlet 204 and a liquid outlet 206, the gas outlet 204 being connected with the injection port 166, the liquid outlet 206 being connected with the first port 12 and an inlet of the outdoor heat exchanger 10, respectively; a throttling assembly 22 including a first end connected with the refrigerant inlet 202, and a second end connected with the second port 14; a first pipe 24 including a first end connected with an outlet of the outdoor heat exchanger 10, and a second end arranged between the throttling assembly 22 and the second port 14.

The two-pipe enhanced-vapor-injection outdoor unit provided by the present disclosure includes the outdoor heat exchanger 10, the first port 12, the second port 14, the enhanced-vapor-injection compressor 16, the reversing assembly 18, the flash evaporator 20, the throttling assembly 22 and the first pipe 24. The first end of the reversing assembly 18 is connected with the gas discharge port 162, and the second end of the reversing assembly 18 is connected with the gas return port 164. The gas outlet 204 of the flash evaporator 20 is connected with the injection port 166, and the liquid outlet 206 of the flash evaporator 20 is connected with the first port 12 and the inlet of the outdoor heat exchanger 10, respectively. The refrigerant inlet 202 of the flash evaporator 20 is connected with the first end of the throttling assembly 22, and the second end of the throttling assembly 22 is connected with the second port 14. The first end of the first pipe 24 is connected with the outlet of the outdoor heat exchanger 10, and the second end of the first pipe 24 is arranged between the throttling assembly 22 and the second port 14. In the present disclosure, by using the enhanced-vapor-injection compressor 16, the gaseous refrigerant flowing out of the enhanced-vapor-injection heat exchanger directly enters the compressor through the middle injection port 166 of the compressor for the enhanced-vapor-injection compression. Moreover, the flash evaporator 20 and the throttling assembly 22 are added to significantly increase a refrigerant circulation in a heating operation at a low temperature, such that a range of the heating operation at the low temperature is expanded in the two-pipe enhanced-vapor-injection outdoor unit, and also the heating capacity is improved significantly, so as to achieve purposes of improving the cooling capacity at a high temperature and reducing an exhaust superheat degree.

In addition, the first pipe 24 is added, such that the effect of enhanced vapor injection can be obtained in four modes, namely, a cooling mode, a heating mode, a main cooling mode and main heating mode.

The flash evaporator 20 is a container that can hold the refrigerant, and usually has three ports, namely the refrigerant inlet 202 for entrance of the refrigerant gas-liquid mixture, the gas outlet 204 for the refrigerant and the liquid outlet 206 for the refrigerant. The flash evaporator 20 has following working principles: the gas-liquid mixture of the refrigerant from the upstream throttling element flows in through the refrigerant inlet 202 of the flash evaporator 20; due to the sudden expansion of the volume, a large amount of refrigerant flashes out from the liquid refrigerant, becomes the refrigerant gas with a low temperature, and flows out of the gas outlet 204; and the liquid refrigerant which has not flashed flows out of the flash evaporator 20 from the liquid outlet 206. Thus, there are not any droplets at the gas outlet 204 of the flash evaporator 20, and there is not any gas at the liquid outlet 206.

Since the gas outlet 204 of the flash evaporator 20 is connected to the injection port 166, it can be ensured that the refrigerant discharged from the gas outlet 204 is a gaseous refrigerant during the enhanced vapor injection, which effectively prevents the problem of liquid impact of the enhanced-vapor-injection compressor 16, and guarantees the service life of the enhanced-vapor-injection compressor 16.

The two-pipe enhanced-vapor-injection outdoor unit is a two-pipe structure, and two connection pipes are provided between an indoor unit and the outdoor unit. That is, the first port 12 and the second port 14 are used to be connected with the indoor unit. Compared with the three-pipe multi-split system in the related art, the two-pipe heat-recovery multi-split system provided by the present disclosure has a simple structure, such that the cupper materials are saved, and the mounting cost is reduced.

In addition, the two-pipe enhanced-vapor-injection outdoor unit provided by the present disclosure is used in the two-pipe enhanced-vapor-injection multi-split system, and the multi-split system is a heat-recovery multi-split system. The heat recovery means that the heat discharged from the cooling room is recovered for heating of the heating room. Specifically, the system uses the indoor-unit heat exchanger to absorb heat from the cooling room, then the indoor-unit heat exchanger releases such heat completely or partially to the heating room for heating, and the heat lacked by the system or the remaining heat of the system is obtained from the environment by the outdoor-unit heat exchanger. However, for the ordinary heat-pump multi-split system, the heat required by the heating indoor unit totally comes from the heat absorption and the power consumption of the outdoor-unit heat exchanger. Thus, compared with the ordinary heat pump, the heat-recovery multi-split system has a significant energy-saving effect.

The heat-recovery multi-split system includes four operation modes, namely a cooling mode, a main cooling mode, a main heating mode and a heating mode. When all the operating indoor units are in the cooling mode/the heating mode, the outdoor unit operates in the cooling mode/the heating mode. When a part of the operating indoor units are in the cooling mode, another part of the operating indoor units are in the heating mode, and the cooling load is greater than the heating load, the outdoor unit will operate in the main cooling mode. When a part of the operating indoor units are in the cooling mode, another part of the operating indoor units are in the heating mode, and the cooling load is less than the heating load, the outdoor unit will operate in the main heating mode. If the flow rate required for running the cooling indoor units is exactly equal to the flow rate required for running the heating indoor units, the system operates in a full heat-recovery mode.

In an embodiment provided by the present disclosure, preferably, the third end of the reversing assembly 18 is switchably connected to the inlet of the outdoor heat exchanger 10 or the outlet of the outdoor heat exchanger 10, and the fourth end of the reversing assembly 18 is switchably connected to the second port 14 or the first port 12.

In this embodiment, the third end of the reversing assembly 18 is switchably connected to the inlet of the outdoor heat exchanger 10 or the outlet of the outdoor heat exchanger 10, and the fourth end of the reversing assembly 18 is switchably connected to the second port 14 or the first port 12. When the two-pipe enhanced-vapor-injection multi-split system is in the cooling mode and the main cooling mode, the third end of the reversing assembly 18 is connected to the inlet of the outdoor heat exchanger 10, and the fourth end of the reversing assembly 18 is connected to the second port 14. When the two-pipe enhanced-vapor-injection multi-split system is in the heating mode and the main heating mode, the third end of the reversing assembly 18 is connected to the outlet of the outdoor heat exchanger 10, and the fourth end of the reversing assembly 18 is connected to the first port 12, so as to achieve different flow directions of the refrigerant.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a first solenoid valve 26 arranged the gas outlet 204 and the injection port 166, and having a conduction direction from the gas outlet 204 to the injection port 166.

In this embodiment, the two-pipe enhanced-vapor-injection outdoor unit includes the first solenoid valve 26. The first solenoid valve 26 is conducted when powered on, and is closed when powered off. When the first solenoid valve 26 is powered on to be conducted, the conduction direction of the first solenoid valve 26 is from the gas outlet 204 to the injection port 166, i.e. a conduction direction, in which the refrigerant is only allowed to flow from the gas outlet 204 to the injection port 166, so as to avoid the refrigerant backflow phenomenon.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes a first check valve 28 disposed in the first pipe 24, and the first check valve 28 has a conduction direction from the outlet of the outdoor heat exchanger 10 to the throttling assembly 22.

In this embodiment, by adding the first pipe 24, the outlet of the outdoor heat exchanger 10 and the throttling assembly 22 are connected. The first check valve 28 is arranged in the first pipe 24, and is added between the outlet of the outdoor heat exchanger 10 and the throttling assembly 22, so as to prevent the gas from being exchanged between the outlet of the outdoor heat exchanger 10 and the throttling assembly 22 during heating, such that only in the cooling mode and the main cooling mode, the refrigerant flowing out of the outlet of the outdoor heat exchanger 10 is allowed to flow through the first check valve 28 into the throttling assembly 22, while in the heating mode and the main heating mode, the first check valve 28 is closed, and thus the refrigerant flowing out of the outlet of the outdoor heat exchanger 10 cannot pass through the first pipe 24.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a second check valve 30, the second check valve 30 connecting the first port 12 with the liquid outlet 206, and having a conduction direction from the liquid outlet 206 to the first port 12; and a third check valve 32, the third check valve 32 connecting the second port 14 to the throttling assembly 22, and having a conduction direction from the second port 14 to the throttling assembly 22.

In this embodiment, the two-pipe enhanced-vapor-injection outdoor unit includes the second check valve 30, and the conduction direction of the second check valve 30 is form the liquid outlet 206 to the first port 12. A first end of the second check valve 30 is arranged between the liquid outlet 206 and the inlet of the outdoor heat exchanger 10, and a second end of the second check valve 30 is connected with the first port 12. In the cooling mode and the main cooling mode, the second check valve 30 is turned on, such that the refrigerant flowing out of the liquid outlet 206 of the flash evaporator 20 flows through the second check valve 30 to the first port 12. In the heating mode and the main heating mode, the second check valve 30 is closed, and the refrigerant flowing out of the liquid outlet 206 of the flash evaporator 20 cannot pass through the second check valve 30, but can only pass through the inlet of the outdoor heat exchanger 10.

Further, the two-pipe enhanced-vapor-injection outdoor unit includes the third check valve 32, and the conduction direction of the third check valve 32 is from the second port 14 to the throttling assembly 22. In the heating mode and the main heating mode, the third check valve 32 is turned on, and the refrigerant flowing out of the second port 14 passes through the third check valve 32 to the throttling assembly 22. In the cooling mode and the main cooling mode, the third check valve 32 is closed, and the refrigerant flowing out of the first pipe 24 can only flow to the throttling assembly 22.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a fourth check valve 34, the fourth check valve 34 connecting the second port 14 to the fourth end of the reversing assembly 18, and having a conduction direction from the second port 14 to the fourth end of the reversing assembly 18; and a fifth check valve 36, the fifth check valve 36 connecting the first port 12 to the fourth end of the reversing assembly 18, and having a conduction direction from the fourth end of the reversing assembly 18 to the first port 12.

In this embodiment, the two-pipe enhanced-vapor-injection outdoor unit includes the fourth check valve 34 and the fifth check valve 36. The fourth check valve 34 connects the second port 14 to the fourth end of the reversing assembly 18, and the conduction direction of the fourth check valve 34 is from the second port 14 to the fourth end of the reversing assembly 18. The fifth check valve 36 connects the first port 12 to the fourth end of the reversing assembly 18, and the conduction direction of the fifth check valve 36 is from the fourth end of the reversing assembly 18 to the first port 12. During operations in the cooling mode and the main cooling mode, the fourth check valve 34 is conducted, and the fifth check valve 36 is closed. During operations in the heating mode and the main heating mode, the fifth check valve 36 is conducted, and the fourth check valve 34 is closed.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a sixth check valve 38, the sixth check valve 38 connecting the third end of the reversing assembly 18 to the inlet of the outdoor heat exchanger 10, and having a conduction direction from the third end of the reversing assembly 18 to the outdoor heat exchanger 10; and a seventh check valve 40, the seventh check valve 40 connecting the third end of the reversing assembly 18 to the outlet of the outdoor heat exchanger 10, and having a conduction direction from the outlet of the outdoor heat exchanger 10 to the third end of the reversing assembly 18.

In this embodiment, the two-pipe enhanced-vapor-injection outdoor unit includes the sixth check valve 38 and the seventh check valve 40. The sixth check valve 38 and the fifth check valve 36 are both connected with the third end of the reversing assembly 18, and the other ends of the sixth check valve 38 and the seventh check valve 40 are connected with the inlet of the outdoor heat exchanger 10 and the outlet of the outdoor heat exchanger 10, respectively. During operations in the cooling mode and the main cooling mode, the sixth check valve 38 is conducted, and the seventh check valve 40 is closed. During operations in the heating mode and the main heating mode, the seventh check valve 40 is conducted, and the sixth check valve 38 is closed.

In an embodiment provided by the present disclosure, preferably, the throttling assembly 22 includes at least one throttling device 222 and at least one eighth check valve 224 connected in series, and the eighth check valve 224 has a conduction direction from the second port 14 to the refrigerant inlet 202.

In this embodiment, the throttling assembly 22 includes the at least one throttling device 222 and the at least one eighth check valve 224 connected in series. The conduction direction of the eighth check valve 224 is from the supercooler to the inlet of the outdoor heat exchanger 10. One throttling device 222 may be connected in series with one eighth check valve 224, or one throttling device 222 may be connected in series with a plurality of eighth check valves 224, or a plurality of throttling devices 222 may be connected in series with one eighth check valve 224, so as to ensure the effects of throttling and depressurization, and thus a better depressurization effect can be achieved after multi-stage depressurizations.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes: a second pipe connecting the gas discharge port 162 to the first port 12; and a second solenoid valve 42 arranged in the second pipe, and having a conduction direction from the gas discharge port 162 to the first port 12.

In this embodiment, the two-pipe enhanced-vapor-injection outdoor unit includes the second pipe and the second solenoid valve 42 arranged in the second pipe. During the operation in the cooling mode, the second solenoid valve 42 is closed, and all the refrigerant discharged from the gas discharge port 162 passes through the third end of the reversing assembly 18 into the inlet of the outdoor heat exchanger 10. During the operation in the main cooling mode, the second solenoid valve 42 is turned on, a part of the refrigerant discharged from the gas discharge port 162 passes through the third end of the reversing assembly 18 into the inlet of the outdoor heat exchanger 10, and another part of the refrigerant discharged from the gas discharge port 162 passes through the second solenoid valve 42 into the first port 12, so as to ensure that the two-pipe enhanced-vapor-injection multi-split system can achieve the cooling mode and the main cooling mode.

In an embodiment provided by the present disclosure, preferably, the two-pipe enhanced-vapor-injection outdoor unit includes a ninth check valve 44, the ninth check valve 44 connects the inlet of the outdoor heat exchanger 10 to the liquid outlet 206, and has a conduction direction from the liquid outlet 206 to the inlet of the outdoor heat exchanger 10.

In this embodiment, the two-pipe enhanced-vapor-injection outdoor unit includes the ninth check valve 44, and the conduction direction of the ninth check valve 44 is from the liquid outlet 206 to the inlet of the outdoor heat exchanger 10. In the cooling mode and the main cooling mode, the ninth check valve 44 is closed, and the refrigerant flowing out of the liquid outlet 206 of the flash evaporator 20 cannot pass through the ninth check valve 44 into the inlet of the outdoor heat exchanger 10, but can only pass through the pipe, where the second check valve 30 is, into the first port 12. In the heating mode and the main heating mode, the ninth check valve 44 is turned on, and the refrigerant flowing out of the liquid outlet 206 of the flash evaporator 20 passes through the ninth check valve 44 into the inlet of the outdoor heat exchanger 10.

According to an aspect of the present disclosure, a two-pipe enhanced-vapor-injection multi-split system is provided. The two-pipe enhanced-vapor-injection multi-split system includes the two-pipe enhanced-vapor-injection outdoor unit according to any of the above embodiments. Therefore, the two-pipe enhanced-vapor-injection multi-split system has all the significant effects of the two-pipe enhanced-vapor-injection outdoor unit according to any of the above embodiments.

The two-pipe enhanced-vapor-injection multi-split system includes a refrigerant-flow-direction switching device 48, and the refrigerant-flow-direction switching device 48 includes a gas-liquid separator 50 for shunting of the gas-liquid two-phase refrigerant. A plate heat exchanger is used for obtaining a supercooling degree of a liquid refrigerant. Multiple groups of solenoid valves are used to switch the flow direction of the refrigerant.

As illustrated in FIG. 3, during cooling, the high-temperature and high-pressure gaseous refrigerant comes out of the enhanced-vapor-injection compressor 16, passes through the reversing assembly 18 and the sixth check valve 38, and then flows through the outdoor heat exchanger 10 to be condensed into the high-pressure liquid refrigerant. A part of the high-pressure liquid refrigerant passes through the throttling assembly 22 to be throttled and depressurized into the two-phase refrigerant, and the two-phase refrigerant enters the flash evaporator 20. The gaseous refrigerant passes through the first solenoid valve 26 into the injection port 166 of the enhanced-vapor-injection compressor 16. Another part of the liquid refrigerant passes through the second check valve 30 to the first port 12 (an output pipe), and further enters an inlet of the gas-liquid separator 50 of the refrigerant-flow-direction switching direction 48.

As illustrated in FIG. 4, during heating, the high-temperature and high-pressure gaseous refrigerant comes out of the enhanced-vapor-injection compressor 16, passes through two paths, i.e. the second solenoid valve 42 as well as the reversing assembly 18 and the fifth check valve 36, to the high pressure valve, respectively, then flows from the high pressure valve to the inlet of the refrigerant-flow-direction switching device 48 through the first port 12 (the output pipe of the outdoor unit), further enters the gas-liquid separator 50, and then enters the two-pipe enhanced-vapor-injection indoor unit 46 through the gas pipe from a gas outlet of the gas-liquid separator 50 after passing through the heating solenoid valve. After being condensed into the high-pressure liquid refrigerant in the two-pipe enhanced-vapor-injection indoor unit 46, the refrigerant flows through the electronic expansion valve of the indoor unit, and becomes the high-pressure two-phase refrigerant. The high-pressure two-phase refrigerant flows through the throttling element (whose opening is maintained to be fully opened so as to reduce the resistance as much as possible) of the refrigerant-flow-direction switching device 48, returns to the second port 14 (an input pipe of the outdoor unit), passes through the low pressure valve into the two-pipe enhanced-vapor-injection outdoor unit, further passes through the main throttling assembly 22 of the outdoor unit and then enters the inlet of the flash evaporator 20 after passing through the third check valve 32. After flowing out of the liquid outlet 206, a liquid part of the refrigerant enters the outdoor heat exchanger 10 to absorb heat, further passes through the reversing assembly 18, returns to a low-pressure tank, and then enters the gas return port 164 of the enhanced-vapor-injection compressor 16. After flowing out of the gas outlet 204 of the flash evaporator 20, another gaseous part of the refrigerant enters a compression chamber of the enhanced-vapor-injection compressor 16 through the first solenoid valve 26.

As illustrated in FIG. 5, during main cooling, the high-temperature and high-pressure gaseous refrigerant comes out of the enhanced-vapor-injection compressor 16, a part of the high-temperature and high-pressure gaseous refrigerant passes through the reversing assembly 18 and the sixth check valve 38, and further flows through the outdoor heat exchanger 10 to be condensed into the high-pressure liquid refrigerant. A part of the high-pressure liquid refrigerant passes through the throttling assembly 22 to be throttled and depressurized into the two-phase refrigerant. The two-phase refrigerant enters the flash evaporator 20, and the gaseous refrigerant passes through the first solenoid valve 26 into the injection port 166 of the enhanced-vapor-injection compressor 16. Another part of the liquid refrigerant passes through the second check valve 30 to the first port 12, and is mixed with another part of the high-temperature and high-pressure gaseous refrigerant, which comes out of the enhanced-vapor-injection compressor 16 and passes through the second solenoid valve 42, into the high-temperature and high-pressure tow-phase refrigerant, and enters the inlet of the gas-liquid separator 50 of the refrigerant-flow-direction switching direction 48. The gaseous refrigerant comes out of the gas outlet, flows through the heating solenoid valve, enters the gas pipe of the heating two-pipe enhanced-vapor-injection indoor unit 46, further flows into the heating two-pipe enhanced-vapor-injection indoor unit 46 to be condensed, then returns to an inlet of a second supercooler 54 of the refrigerant distributor after passing through the throttling element of the two-pipe enhanced-vapor-injection indoor unit 46, further is mixed with the liquid refrigerant coming out of the liquid outlet of the gas-liquid separator 50 and being supercooled by the first supercooler 52, and then enters the cooling two-pipe enhanced-vapor-injection indoor unit 46 after being further supercooled by the second supercooler 54. After being depressurized by the throttling element of the cooling two-pipe enhanced-vapor-injection indoor unit 46, the refrigerant evaporates and absorbs heat in the cooling two-pipe enhanced-vapor-injection indoor unit 46, and becomes the low-pressure gaseous refrigerant. Then, the low-pressure gaseous refrigerant returns to the second port 14 of the two-pipe enhanced-vapor-injection outdoor unit through the cooling solenoid valve. The refrigerant further passes through the fourth check valve 34 and the reversing assembly 18, returns to the low-pressure tank ACC, and then flows back to the gas return port 164 of the enhanced-vapor-injection compressor 16.

As illustrated in FIG. 6, during main heating, the high-temperature and high-pressure gaseous refrigerant comes out of the enhanced-vapor-injection compressor 16, passes through two paths, i.e. the second solenoid valve 42 as well as the reversing assembly 18 and the fifth check valve 36, to the high pressure valve, respectively, then flows from the high pressure valve to the inlet of the refrigerant-flow-direction switching device 48 through the first port 12, and further enters the gas-liquid separator 50. The high-pressure gaseous refrigerant comes out of the gas outlet of the gas-liquid separator 50, passes through the heating solenoid valve, and enters the heating two-pipe enhanced-vapor-injection indoor unit 46 through the gas pipe. The condensed high-pressure liquid refrigerant passes through the electronic expansion valve of the two-pipe enhanced-vapor-injection indoor unit 46 and then flows back to the inlet of the second supercooler 54 of the refrigerant distributor. The refrigerant becomes the high-pressure liquid refrigerant after flowing out of the second supercooler 54 and enters the cooling two-pipe enhanced-vapor-injection indoor unit 44 via the cooling check valve. The refrigerant becomes the medium-pressure two-phase refrigerant after being throttled by the electronic expansion valve, enters the two-pipe enhanced-vapor-injection indoor unit 46 to evaporate and absorb heat, and hence becomes the medium-pressure gaseous refrigerant. The medium-pressure gaseous refrigerant is converged with the medium-pressure two-phase refrigerant flowing through the throttling element of the refrigerant distributor in the low-pressure pipe, and further returns to the two-pipe enhanced-vapor-injection outdoor unit through the second port 14. After passing through the third check valve 32, and further being throttled and depressurized by the throttling assembly 22, the refrigerant enters the inlet of the flash evaporator 20. The liquid refrigerant flows out of the liquid outlet 206, passes through the ninth check valve 44 into the outdoor heat exchanger 10 to evaporate and absorb heat, further flows through the reversing assembly 18 into the low-pressure tank, and then returns to the gas return port 164 of the enhanced-vapor-injection compressor 16. The gaseous refrigerant flows out of the gas outlet 204 of the flash evaporator 20, passes through the first solenoid valve 26, and enters the injection port 166 of the enhanced-vapor-injection compressor 16.

As illustrated in FIG. 7, during cooling, since the two-pipe enhanced-vapor-injection multi-split system increases the enthalpy difference (h_(A-J)>h_(A-I)), it can achieve the same capability with a smaller refrigerant circulation, such that the enhanced-vapor-injection compressor 16 can have a low frequency and make less work, so as to improve the energy efficiency. In addition, since the two-pipe enhanced-vapor-injection multi-split system decreases the exhaust superheat degree (SH<SH′), the enhanced vapor injection can increase the refrigerant circulation and hence improve the cooling capability during the high-temperature cooling.

In the description of the present specification, terms such as “up” and “down” indicate the orientation or position relationship based on the orientation or position relationship illustrated in the drawings only for convenience of description or for simplifying description of the present disclosure, and do not alone indicate or imply that the device or element referred to must have a particular orientation or be constructed and operated in a specific orientation, and hence cannot be construed as a limitation to the present disclosure. The terms “connected,” “mounted,” “fixed” should be understood broadly. For example, “connected” may indicate fixed connections, detachable connections, or integral connections; may also be direct connections or indirect connections via intervening structures, which can be understood by those skilled in the art according to specific situations.

Reference throughout this specification to terms “one embodiment,” “some embodiments,” “a specific example,” “an example” or “some examples,” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, exemplary descriptions of aforesaid terms are not necessarily referring to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

The above embodiments are only preferred embodiments of the present disclosure, and should not be construed to limit the present disclosure. It can be understood by those skilled in the related art that the present disclosure may have various modifications and changes. Any modifications, equivalents, and improvements made without departing from spirit and principles of the present disclosure should be fallen into the protection scope of the present disclosure. 

1. A two-pipe enhanced-vapor-injection outdoor unit, comprising: an outdoor heat exchanger, a first port and a second port; an enhanced-vapor-injection compressor comprising a gas discharge port, a gas return port and an injection port; a reversing assembly comprising a first end connected with the gas discharge port and a second end connected with the gas return port; a flash evaporator comprising a refrigerant inlet, a gas outlet and a liquid. outlet, the gas outlet being connected with the injection port, the liquid outlet being connected with the first port and an inlet of the outdoor heat exchanger, respectively; a throttling assembly comprising a first end connected with the refrigerant inlet and a second end connected with the second port; and a first pipe comprising a first end connected with an outlet of the outdoor heat exchanger and a second end connected between the throttling assembly and the second port.
 2. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the reversing assembly further comprises: a third end switchably connected to the inlet of the outdoor heat exchanger or the outlet of the outdoor heat exchanger; and a fourth end switchably connected to the second port or the first port.
 3. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a first solenoid valve arranged between the gas outlet and the injection port, and having a conduction direction from the gas outlet to the injection port.
 4. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a first check valve arranged in the first pipe, and having a conduction direction from the outlet of the outdoor heat exchanger to the throttling assembly.
 5. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a second check valve connecting the first port to the liquid outlet, and having a conduction direction from the liquid outlet to the first port; and a third check valve connecting the second port to the throttling assembly, and having a conduction direction from the second port to the throttling assembly.
 6. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a fourth check valve connecting the second port to a fourth end of the reversing assembly, and having a conduction direction from the second port to the fourth end of the reversing assembly; and a fifth check valve connecting the first port to the fourth end of the reversing assembly, and having a conduction direction from the fourth end of the reversing assembly to the first port.
 7. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a sixth check valve connecting a third end of the reversing assembly to the inlet of the outdoor heat exchanger, and having a conduction direction from the third end of the reversing assembly to the outdoor heat exchanger; and a seventh check valve connecting the third end of the reversing assembly to the outlet of the outdoor heat exchanger, and having a conduction direction from the outlet of the outdoor heat exchanger to the third end of the reversing assembly.
 8. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the throttling assembly comprises at least one throttling device and at least one eighth check valve connected in series, and the eighth check valve has a conduction direction from the second port to the refrigerant inlet.
 9. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a second pipe connecting the gas discharge port to the first port; and a second solenoid valve arranged in the second pipe, and having a conduction direction from the gas discharge port to the first port.
 10. The two-pipe enhanced-vapor-injection outdoor unit according to claim 1, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a ninth check valve connecting the inlet of the outdoor heat exchanger to the liquid outlet, and having a conduction direction from the liquid outlet to the inlet of the outdoor heat exchanger.
 11. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim
 1. 12. The two-pipe enhanced-vapor-injection outdoor unit according to claim 7, wherein the throttling assembly comprises at least one throttling device and at least one eighth check valve connected in series, and the eighth check valve has a conduction direction from the second port to the refrigerant inlet.
 13. The two-pipe enhanced-vapor-injection outdoor unit according to claim 7, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a second pipe connecting the gas discharge port to the first port; and a second solenoid valve arranged in the second pipe, and having a conduction direction from the gas discharge port to the first port.
 14. The two-pipe enhanced-vapor-injection outdoor unit according to claim 7, wherein the two-pipe enhanced-vapor-injection outdoor unit comprises: a ninth check valve connecting the inlet of the outdoor heat exchanger to the liquid outlet, and having a conduction direction from the liquid outlet to the inlet of the outdoor heat exchanger.
 15. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim
 2. 16. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim 5,
 17. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim
 7. 18. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim
 8. 19. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim
 9. 20. A two-pipe enhanced-vapor-injection multi-split system, comprising a two-pipe enhanced-vapor-injection outdoor unit according to claim
 10. 